1. Field of the Invention
This invention pertains to a control device for engines by which several superchargers are controlled, and more particularly, to a control device by which at least a primary supercharger, which supercharges in a low intake region, a secondary supercharger, which supercharges in a high intake region, and an automatic transmission are controlled.
2. Description of Related Art
Conventionally, some kinds of internal combustion engines for vehicles have at least a primary supercharger, which supercharges in what is known as a low intake region, and a secondary supercharger, which supercharges in what is known as a high intake region. These superchargers are selectively activated and controlled in accordance with previously provided or designed switching patterns for various intake conditions of the engine. Moreover, automatic transmissions are used in combination with engines having such first and second superchargers. Such an engine equipped with first and second, or primary and secondary, superchargers and an automatic transmission is known from, for example, Japanese Patent Application No. 63-258,368, laid open as japanese Unexamined Patent Publication No. 2-108,820 on Apr. 20, 1990.
However, the engine described in the above publication, which is equipped with primary and secondary superchargers and an automatic transmission, produces torque shock upon switching of the superchargers. Such torque shock can be suppressed, via a control device, by precisely controlling the switching of the primary and secondary superchargers, but can not be avoided completely.
Automatic transmissions are typically controlled to shift in accordance with previously provided, particularly designed gear shift patterns. Such gear shift patterns generally vary, depending on vehicle running conditions or vehicle speeds and engine operating conditions or engine speeds. In order for the automatic transmission to be reliable in terms of both gear shift shock and attenuation, gear shift timing must be precisely managed. However, since the control of gear shift timing is performed based on the assumption that engine torque during a gear shift will have reached a value that is estimated based on engine properties, if shifting of the automatic transmission is accompanied by switching of the superchargers, the automatic transmission produces torque shock, due to the torque shock generated on switching of the superchargers. For example, because there are cases in which, during acceleration, switching of the superchargers and shifting of the automatic transmission must be simultaneously controlled, there is a chance that torque shock accompanying switching of the superchargers and torque shock accompanying shifting of the automatic transmission will occur simultaneously.